High Temperature Mechanical Properties Research Articles

High-temperature mechanical properties and radiation resistance properties of reduced-activation high-entropy alloys FeMnCrTi0.1

High-temperature mechanical properties and radiation resistance properties of reduced-activation high-entropy alloys FeMnCrTi0.1

Evaluation of AlCoCrFeNiTi-high entropy alloy (HEA) as top coat material in thermal barrier coating (TBC) system and investigation of its high temperature oxidation behavior

To obtain compatible properties of high-temperature performance and mechanical strength properties, AlCoCrFeNiTi high-entropy alloy (HEA) was designed as a new candidate material for metal-based thermal barrier coating (TBC) systems. The aim of this study is to investigate potential applications of AlCoCrFeNiTi-HEA as a coating material for TBC systems and to determine its behavior under high temperature conditions. CoNiCrAlY bond coatings were produced on the Inconel-718 substrate surface using high-velocity oxygen fuel (HVOF) technique. AlCoCrFeNiTi-HEAs were produced on CoNiCrAlY bond coatings using atmospheric plasma spray (APS) technique and a typical TBC system structure was obtained. The produced AlCoCrFeNiTi-HEA TBC system was exposed to oxidation at temperatures of 1000 °C and 1100 °C for time periods of 5 h, 25 h, 50 h and 100 h in order to determine the oxidation resistance under isothermal conditions and to investigate formation and growth behavior of oxide structures formed at the coating interface. As a result of oxidation tests, the growth behavior of the thermally grown oxide (TGO) layer formed between the coating interfaces and the microstructural changes occurring in the coating system were investigated depending on temperature and time processes. In the TBC system with Ti-containing HEA content, a transformation from body-centered cubic (BCC) structure to rhombohedral crystal lattice structure occurred as a result of increasing temperature. Many spinel compound forms were formed at the coating interface. It was observed that the coating system with AlCoCrFeNiTi-HEA content maintained its structural integrity without any damage such as microstructural and mechanical spalling and cracking under conditions of high temperature and different time periods.

Study on high-entropy rare-earth zirconate ceramics for thermal barrier coatings: High-temperature phase stability, thermophysical and mechanical properties

Study on high-entropy rare-earth zirconate ceramics for thermal barrier coatings: High-temperature phase stability, thermophysical and mechanical properties

Investigating the anisotropic behavior and high-temperature mechanical properties of GH4251 nickel-based superalloy prepared by selective laser melting and post heat treatment

GH4251 nickel-based superalloy prepared by selective laser melting (SLM) exhibits pronounced anisotropy. In this study, the anisotropic behavior and high temperature mechanical properties of SLMed GH4251 superalloy with different solution heat treatment temperatures (1070°C, 1120°C, 1130°C and 1170°C) at 700°C were systematically investigated. The results reveal that there is a temperature inflection point among 1120°C-1130°C, below which GH4251 superalloy shows an obvious {001} texture orientation in the deposition direction, making the alloy exhibit a significantly higher elongation under a comparable tensile strength. Above the inflection point, a large number of secondary γ' phases are precipitated out and the dynamic recrystallization of the superalloy occurs, which significantly reduces the mechanical anisotropy. Additionally, the study delves into the detailed discussion of the strengthening mechanisms of the SLMed GH4251 superalloy.

Room and high temperature mechanical properties of spray co-deposited SiCP/Al-Cu-Mg-Ag composite: Effect of pre-stretching

Room and high temperature mechanical properties of spray co-deposited SiCP/Al-Cu-Mg-Ag composite: Effect of pre-stretching

Microstructure evolution and dynamic recrystallization mechanism of tantalum-tungsten alloys under hot compression

Ta-W alloys exhibit outstanding comprehensive properties at high temperatures, allowing them to have great application prospects in the high-temperature field. High-temperature compression tests (1573~1873 K) were conducted to evaluate the high-temperature mechanical properties of Ta-12W alloy, and the strain-compensated Arrhenius-Type model and hot processing map were developed to predict the optimal processing window. The electron backscatter diffraction, Transmission electron microscope, and DEFORM-3D software were performed to investigate the microstructure evolution and distributions of strain. The results demonstrated that the flow stress of Ta-12W alloy presented apparent negative temperature sensitivity and positive strain rate sensitivity. Based on the thermal processing diagrams and EBSD analysis, the results show that the low deformation temperature and high strain rate introduce stress concentration and deformation instability in the Ta-12W alloy. The optimized processing temperature and strain rate are at 1800 ~1873 K/0.001 s-1~0.05 s-1, and the microstructure at 1873 K/0.001 s-1 is more uniform and exhibits a low residual stress level. As the temperature increases, dynamic recovery and dynamic recrystallization cause significant softening effects, and continuous dynamic recrystallization dominates the high-temperature deformation behavior. Moreover, multiple continuous dynamic recrystallizations occur simultaneously, including sub-grain nucleation inside large grains, sub-grain nucleation at grain boundaries, and grain fragmentation accompanied by grain rotation. This study revealed the mechanisms of microstructural evolution during hot deformation of Ta-12W alloy, providing important guidance for optimizing the thermomechanical processing parameters.

High-Temperature Mechanical Properties of Basalt Fibers: A Step Towards Fire-Safe Materials for Photovoltaic Applications

Amidst the urban energy transition towards clean and renewable energy, distributed photovoltaic (PV) systems are emerging as critical infrastructure. However, the evolution of PV rack and mount systems has lagged, particularly in addressing cost efficiency and fire safety This study focuses on the high-temperature mechanical properties of basalt fibers (BFs), a key component of basalt fiber-reinforced polymer (BFRP), to establish a foundational understanding for future BFRP applications. The experimental results demonstrate that basalt fibers retain approximately 150 MPa residual tensile strength at 600 °C (30–40% of room temperature strength of Q235B steel) and 94 MPa at 800 °C, outperforming steel under similar conditions. Furthermore, the decomposition of wetting agents and Fe2+ oxidation at 600 °C was observed to stabilize after 100 min, maintaining structural integrity. These findings validate the high-temperature performance of BF, paving the way for subsequent studies at the BFRP composite level, which will address structural optimization and fire-resistance strategies for PV rack and mount systems. This research provides a critical step toward improving the safety and sustainability of urban PV systems.

Mechanical properties of bridge steel Q420qE at elevated temperatures

High-temperature mechanical properties of bridge steels, which were rarely investigated, are the foundation for fire resistance analysis and design of bridges. This study investigates the high temperature mechanical properties of Q420qE bridge steel by using steady-state tensile test method. Results indicate that this steel shows no yield plateau at both room temperature and elevated temperatures. Compared with the same grade structural steels, the decrease in elastic modulus and yield strength of Q420qE with increasing temperature are slower. However, the decrease of ultimate strength is more rapid, with a maximum difference on reduction factor being about 0.327 (41.92 %). The mainstream fire resistance design standards exhibit limitations in predicting the high temperature mechanical properties of Q420qE steel. Furthermore, predictive equations of mechanical property reduction factors of Q420qE at elevated temperatures were proposed, and constitutive model of Q420qE at elevated temperatures was recommended.

Experimental study on deformation mechanism around indentation of GH4169 alloy

The GH4169 alloy is widely used in engineering structures due to its excellent high-temperature strength, corrosion resistance, and mechanical properties. However, local stresses during plastic deformation significantly impact its macroscopic mechanical performance. This study investigates the residual deformation fields and plastic deformation mechanisms around local indentations using digital image correlation (DIC), electron backscatter diffraction (EBSD), and nanoindentation. The results show that the indentation rate affects the accumulation of geometrically necessary dislocations (GNDs). Increasing the loading rate from 2 mN/s to 20 mN/s leads to a 32 % increase in GNDs. When the loading strain rate increases from 0.01 s−1 to 0.2 s−1, GNDs increase by 43 %. Moreover, indentations initiate more than two slip systems in the alloy crystals, with slip trace lines consistent with theoretical predictions. The plastic deformation field distribution around the indentations, obtained using DIC, reveals the influence range of slip generation due to indentations to be around 10 μm.

High-temperature mechanical properties and thermal shock resistance of an alumina-fiber-reinforced alumina ceramic matrix composite

An alumina-fiber-reinforced alumina ceramic matrix (Al2O3/Al2O3) composite is fabricated by a slurry infiltration process in this study. The slurry contains Al2O3 powders with broad particle size distribution (d10=0.35 μm, d50=0.57 μm, d90=1.90 μm). The resultant Al2O3/Al2O3 composite exhibits a density of 2.95 ± 0.02 g/cm3 and porosity of 25 ± 1%. Mechanical properties are assessed via three-point flexural tests, revealing a high flexural strength of 400 ± 8 MPa at room temperature. The high-temperature mechanical properties and thermal shock resistance are further examined. The flexural strength remains stable from room temperature to 1100°C, while temperatures up to 1200°C induces superplastic behavior. After thermal shock tests (5, 10 and 20 cycles at 1100°C), the composite maintains a stable microstructure and flexural strength. The Al2O3 powders with broad particle size distribution are beneficial to the high-temperature mechanical properties and thermal shock resistance of the Al2O3/Al2O3 composite.

Microstructure Evolution and High-Temperature Mechanical Properties of Ti-6Al-4Nb-4Zr Fabricated by Selective Laser Melting

Microstructure Evolution and High-Temperature Mechanical Properties of Ti-6Al-4Nb-4Zr Fabricated by Selective Laser Melting

Experimental study on the creep performance of Grade 8.8 and 10.9 high-strength bolts at elevated temperatures

High-strength bolts are widely used in beam-column connections which are typically subjected to significant pretension and experience high stress levels. Under fire conditions, high-strength bolts may exhibit noticeable creep deformation due to the combined effects of high stress and high temperature, which may result in significant deformation of the connection, thereby threatening the stability of the structure. This paper reports an experimental study on the creep behavior of Grade 8.8 and 10.9 high-strength bolts at elevated temperatures. A series of tensile tests are conducted on high-strength bolts at elevated temperatures, and varying stress ratios are set based on the yield strength measured form the tensile tests. Test results indicate that the temperature has significant influence on the mechanical properties of Grade 8.8 and 10.9 high-strength bolts. Through the entire temperature range, current specifications significantly overestimate the yield strength of high-strength bolts at high temperatures. At the same temperature, the development of creep strain over time is positively related to the stress ratio. An increase in stress ratio from 0.4 to 0.6 or 0.8 results in a maximum 7.8-time increase in creep strain. The temperature of 500℃ can be regarded as the critical temperature at which the creep effects of Grade 8.8 and Grade 10.9 high-strength bolts should be considered. The mechanical property prediction equations and a modified creep model for Grade 8.8 and 10.9 high-strength bolts were developed, which have high reliability in predicting the high-temperature mechanical properties and creep behavior of high-strength bolts.

Microstructure and mechanical properties at elevated temperatures of as-built and heat-treated Inconel 718 produced through laser powder bed fusion processes

Purpose This study aims to better understand the influence of various post-treatments on the microstructure and mechanical properties of additively manufactured parts for critical applications. Design/methodology/approach In this study, Laser Powder Bed Fusion (LPBF) fabricated Inconel 718 (IN718) samples were subjected to various heat treatments, namely homogenization, solution heat treatment and double aging, to investigate their influence on the microstructure, mechanical properties and fracture mechanism at an elevated temperature of 650 °C. Homogenization treatment was performed at 1080 °C for durations ranging from 1–8 h. The solution treatment temperature varied from 980 °C to 1140 °C for 1 h, followed by double aging treatment. Findings At 650 °C, the as-built sample showed the minimum strength but demonstrated the maximum elongation to failure compared to the heat-treated samples. The strength of the IN718 superalloy increased by 20.26% to 34.81%, while ductility significantly reduced by 65.26% to 72.89% after various heat treatments compared to the as-built state. This change is attributed to the enhancement in grain boundary strength resulting from the pinning effect of the intergranular δ-phase. Originality/value The study observed that the variations in the fracture mechanism of LPBF fabricated IN718 depend on the duration and temperature of heat treatment. This research provides a thorough overview of the high-temperature mechanical properties of LPBF fabricated IN718 subjected to different homogenization times and solution treatment temperatures, correlating these effects to the corresponding changes in microstructure.

Effect of the synergistic effect of Cr and Mo on the solidification microstructure and mechanical properties of NiAl-based high-entropy alloys

To balance the strength and toughness of NiAl-based alloys by coupling multiple strengthening mechanisms, two novel high-entropy alloys (HEAs), Ni0.35Al0.3 (CoFe)0.2Cr0.15-xMox (x=0,0.05), were prepared, and their mechanical properties were explored. First, the addition of Mo induces the shape of the precipitate to change from spherical to acicular. Ni0.35Al0.3(CoFe)0.2Cr0.1Mo0.05 has excellent high-temperature mechanical properties. Foremost, the strength is better than that of most Ni-based superalloys, Co-based superalloys and Ni-Co-based superalloys at 873 K. Notably, its yield strength is greater than 1400 MPa. When the temperature reaches 1123 K, the yield strength is still greater than 600 MPa. Moreover, the acicular precipitated phase maintains a co-lattice relationship with the matrix. The synergistic effect of solid solution strengthening and precipitation strengthening significantly enhances the strain hardening ability of the Ni0.35Al0.3 (CoFe)0.2Cr0.1Mo0.05 alloy.

Embedding thermostable rGO/SiCxOy composite phase in SiC fibers for improved high temperature resistance

Silicon carbide (SiC) fibers exhibit exceptional potential in harsh environment applications such as aerospace and nuclear energy. However, the high temperature mechanical properties of SiC fibers are still limited by the unmanageable microstructure. Herein, we propose an amorphous phase stabilizing strategy by embedding thermostable reduced graphene oxide/silicon oxycarbide (rGO/SiCxOy) composite phase in SiC fibers via the polymer-derived ceramic (PDC) method. Homodisperse vinyl-bridged graphene oxide/polycarbosilane (PCS) precursor is designed to transform into rGO/SiC fibers, accompanied by the formation of a more stable rGO/SiCxOy composite structure that intersperses between SiC grains. Additionally, the rGO plays a role in suppressing the decomposition of SiCxOy and the rapid growth of SiC grains at elevated temperatures. As a result, the tensile strength of as-received 0.5%-rGO/SiC (2.64 GPa) and 1%-rGO/SiC (2.28 GPa) fibers are elevated by 40 % and 21 % respectively. Noteworthily, 1%-rGO/SiC fibers maintain a tensile strength of 0.57 GPa even after undergoing 1700 °C heat treatment, while the 0%-rGO/SiC fibers have nearly lost mechanical strength after annealing at 1600 °C. Consequently, the rGO exhibits significant potential for improving the high temperature resistance of ceramic fibers.

Effect of γ′ size on the high-temperature low-stress creep of nickel-based single-crystal superalloys

Nickel-based single crystal superalloys exhibit excellent high temperature mechanical properties due to their unique γ′-γ dual phase microstructure. Microstructure design is the major strategy for increasing their properties. However, the design strategy for the size of the γ′ phase is still lacking. This work investigates the effect of γ′ cuboid size on the creep-rupture life of nickel-based single crystal superalloys via a comparative experiment of two alloys of similar γ′ phase volume fractions and different elemental compositions. The alloy with smaller γ′ phase cuboids exhibits a creep-rupture life twice as long as the alloy with an average cuboid size 30 % larger. In addition, a smaller average γ′ phase cuboid size also contributes to a lower density of the dislocations, a smaller spacing of the raft and lower content of the topologically closed packed phases. The reasons behind these different mechanical properties and microstructures are discussed.

Directed energy deposited Fe36Ni35Al17Cr10Mo2 eutectic high entropy alloy: Hierarchical microstructure and tensile properties

Eutectic high entropy alloy (EHEA) has attracted much attention due to its outstanding properties, which are commonly fabricated through conventional manufacturing methods. Additive manufacturing (AM) techniques that can create near-net components provide opportunities for rapid prototyping EHEAs. This study elucidated the microstructural evolution mechanisms of Fe36Ni35Al17Cr10Mo2 EHEA fabricated by directed energy deposition (DED) via XRD, SEM, and EBSD. The dual-phase dendrite structure, micro-scale heterogeneous grains, and nano-scale BCC phases collectively formed the hierarchical microstructure in the DEDed alloy. We used neutron diffraction to demonstrate texture components and their relation to mechanical behaviors. {013}<100> texture possesses the highest Schmid factor compared to other textures, causing texture-induced softening of the FCC and B2 phases during tension. {233}<0 1‾ 1> texture exhibits the low SF and hard orientation for the B2 phase. Due to the synergistic plastic deformation between FCC and B2 phases and precipitation strengthening from the BCC phases, the DEDed Fe36Ni35Al17Cr10Mo2 exhibits an ultimate strength of ∼1267 MPa with an elongation of ∼20.1 % at room temperature. Moreover, the elevated-temperature tensile testing and crack analysis were employed to indicate the elevated-temperature fracture behaviors. We found that the nucleation and propagation of microcracks were suppressed at the phase boundary at elevated temperatures, avoiding brittleness and achieving excellent high-temperature mechanical properties. These results are expected to open ever-bright prospects for additive manufacturing Co-free high-performance EHEAs.

Improvement of high-temperature strength of Al-4.5Cu alloys by Sc addition through thermally stable phase

The microstructure and high-temperature mechanical properties of Al-4.5Cu alloy, and alloys with Sc addition of 0.1%, 0.2%, and 0.4% were studied. The addition of Sc generates high-temperature stable phase – W phase along the grain boundary, which consumes Cu in the matrix and decrease the θ′ after T6 treatment. However, Sc stabilizes the θ′ precipitate during 300°C exposure and contributes to the high temperature strength by Orowan mechanism. The high-temperature performance of Al-4.5Cu alloy is improved and the strength first increases and then decreases with increasing content of Sc, with optimal content of Sc being 0.2%. The tensile strength of 0.2%Sc alloy at 300°C reaches 158 ± 3 MPa, which is 28 ± 3 MPa higher than that of Sc-free alloy.

Single-crystal structure formation in laser directed energy deposited Inconel 718 through process parameter optimization and substrate orientation tuning

A transverse grain boundary perpendicular to the applied loading direction is normally considered a main reason for the deterioration of the mechanical properties of nickel-based superalloys at high temperatures. Therefore, reducing or even eliminating these types of grain boundaries can effectively delay failure and improve high-temperature mechanical properties. In this study, the feasibility of process parameter optimization and substrate rotation was explored for fabricating single-crystal Inconel 718 specimens during laser directed energy deposition (LDED). The study determined that optimizing the process parameters was dependent on the ability to enlarge the [001] region at the bottom of the melt pool as much as possible. Simultaneously, ensuring that the remelting depth exceeded the stray grain region height at the top of the melt pool was necessary. Therefore, that the stray grains can be fully erased during the subsequent deposition process. Accordingly, an Inconel 718 single-walled specimen (height: 20 mm) with a full single-crystal structure was successfully fabricated using LDED for the first time. However, this approach remains insufficient for fabricating a block with a single-crystal structure, as SGs appear readily in the overlapping regions. Substrate rotation was further considered, where ensuring that one side of the melt pool was in the [001]-grain region was critical. Although the other side of the melt pool featured SGs, they were eliminated through the following overlapping process, as the SG region in the current melt pool corresponded to the [001]-grain region in the next melt pool. Through these two approaches, a small-format single-crystal block with dimensions of 27 × 8.3 × 1.3 mm (length × width × height) was successfully fabricated. Because the Inconel 718 superalloy is not specifically designed for single-crystal structure generation, a large-format block with a single-crystal structure still cannot be fabricated using these approaches. Nevertheless, the findings remain insightful because they demonstrate a wider range of variable microstructures achievable with additive manufacturing processes than with traditional forming processes such as casting or forging and may provide more opportunities for improving the mechanical properties. In addition, the preparation of a small-format single-crystal structure has significant applications in repairing damaged components such as aeroengine blades.

The Customized Heat Treatment for Enhancing the High-Temperature Durability of Laser-Directed Energy Deposition-Repaired Single-Crystal Superalloys.

The high-temperature durability performance plays a crucial role in the applications of single-crystal (SX) superalloys repaired by laser-directed energy deposition (L-DED). A specialized heat treatment process for L-DED-repaired SX superalloys was developed in this study. The effect of the newly customized heat treatment on the microstructure and high-temperature mechanical properties of DD32 SX superalloy repaired by L-DED was investigated. Results indicate that the repaired area of the newly customized heat treatment specimen still maintained a SX structure, the average size of the γ' phase was 236 nm, and the volume fraction was 69%. Obviously recrystallized grains were formed in the repair area of the standard heat treatment specimens, and carbide precipitated along the grain boundary. The size of the γ' phase was about 535 nm. The high-temperature durable life of the newly custom heat treatment specimen was about 19.09 h at 1000 °C/280 MPa, the fracture mode was microporous aggregation fracture, and the fracture location was in the repair area. The durable life of the standard heat treatment specimen was about 8.70 h, the fracture mode was cleavage fracture, and the fracture location was in the matrix area. The crack source of both specimens was interdendrite carbide.